1. Field of the Invention
The present invention relates to semiconductor device electronics in the areas of semiconductor-based logic, magnetoresistive devices, and magnetic sensor technology. The present invention includes a spin resonant tunnel diode and spin transistor that operate by controlling spin-polarized current flow using low applied voltages and/or magnetic fields (for magnetic field sensing only), and which are fabricated using traditional III-V semiconductors (i.e. no magnetic materials). These devices represent an improvement over conventional semiconductor device technology.
2. Description of the Related Art
The prospect of developing semiconductor electronic devices that exploit electron spin has motivated a broad research effort into the spin-related properties of semiconductor materials. Semiconductor spintronics has been identified as an emerging research direction for logic applications due to possible improvements in power consumption, which represents a fundamental limitation in scaling for silicon-based CMOS technologies beyond the next decade. Spin-based devices may also be applied to other semiconductor technologies (e.g. memory, optoelectronics, and quantum computation) with the possibility for enhanced performance and functionality (e.g. nonvolatility, high-speed, and high scalability).
Several spintronic device concepts have been proposed; however, the majority of these rely on magnetic metals or magnetic semiconductors (e.g. diluted magnetic or paramagnetic semiconductors). However, devices relying only on nonmagnetic materials are more attractive for practical application because they are more easily integrated into traditional device architectures, and they avoid the complex fabrication issues associated with the incorporation of magnetic materials (e.g. low magnetic solubility, low-temperature growth, conductivity mismatch, interface quality). Devices that avoid magnetic semiconductor materials also offer greater promise for operation at or above room temperature. Furthermore, devices in which the electron spin state is controlled using applied electric fields (rather than external magnetic fields) are favorable because electric fields may be modulated at high rates. Additionally, stray field effects are much less problematic for device operation when only electric fields are used.
An effective approach in developing spin-based semiconductor devices that do not require magnetic materials is to exploit the spin-orbit interaction in traditional III-V semiconductors, by which an electron with a non-zero momentum will experience an electric field also as an effective magnetic field (or pseudomagnetic field). The electric field causing this pseudomagnetic field may originate from a variety of sources, for example, (i) internal electric fields associated with the polar bonds in III-V semiconductors (bulk inversion asymmetry, BIA); or (ii) extrinsic electric fields introduced through asymmetric layer growth, differences in interface potential on two sides of a semiconductor quantum well layer, or the application of an electric bias to a gate above the semiconductor (structural inversion asymmetry, SIA, also known as the Rashba effect). Each of these sources of electric fields contributes to the total pseudomagnetic field experienced by the electrons. In a spin-based device, this pseudomagnetic field may be used to manipulate electron spin dynamically, through the application of a controllable electric field using a between spin control efficiency and spin relaxation; and (ii) being constrained to ballistic device geometries.